PROJECT SUMMARY/ABSTRACT Mitochondria play a well-established role in regulating metabolism and maintaining cellular homeostasis. Mitochondrial dysfunction has been described in aged cells and organisms, suggesting that it may contribute to the age-related decline in physiologic integrity. However, our understanding of mitochondria?s role in aging is limited by our incomplete characterization of mitochondrial processes and proteins ? a fact highlighted by the limited mitochondrial interventions to improve human healthspan. Thus, the development of new approaches relies on a complete understanding of the biochemical processes that occur within mitochondria. However, many mitochondrial processes and proteins remain unknown or poorly characterized. Thus, elucidating these unknowns in mitochondrial biochemistry will allow for a better understanding of mitochondrial function and its role in the aging process. Coenzyme Q (CoQ) is a mitochondrial lipid that is critical for many processes, including oxidative phosphorylation. Despite its importance to metabolism and mitochondrial function, the biosynthetic pathway for CoQ remains incompletely defined. Defects in this pathway affect CoQ abundance and can disrupt cellular metabolism. Changes in CoQ abundance have been shown to affect longevity and healthspan in animal models, though the specific effects are poorly understood. The mechanisms by which CoQ contribute to aging remain largely obscure, in part due to our limited knowledge of CoQ biosynthesis. Thus, a goal of the proposed research is gain a better understanding of this biosynthetic pathway. Allylic pyrophosphates (APPs) are a class of charged metabolites that are precursors for CoQ?s hydrophobic tail. Given their charge, it is hypothesized that there is a transporter protein for APPs. However, such a transporter has not been identified to date. Thus, the proposed research will utilize yeast genetics and an APP uptake assay to identify and characterize this transporter. The specific aims are to (1) identify candidate APP transporters using CoQ-depdent phenotypes, and (2) define the kinetics of mitochondrial APP uptake in vitro. Successful completion of the proposed aims will provide insight into the mechanisms of APP transport, a vital step in CoQ biosynthesis. Additionally, it enables further investigation into the APP transporter?s potential role in CoQ deficiency, metabolic dysfunction, and aging. The proposed research will be carried out as part of a training plan developed with Dr. Pagliarini at UW- Madison. It is characterized by a robust foundation in the biochemical sciences, opportunities for written and oral communication, strong mentorship, a collegial lab culture, and a supportive training environment at UW-Madison. Important to this plan is the integration with medical school through longitudinal clinical experiences. Altogether, this training plan and research proposal will ensure a rigorous medical and research education ideal for an aspiring physician-scientist.